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ISRO Scientist ME 2017 Paper

Option 2 : Sc/Pr

ST 1: Strength of Materials

2415

15 Questions
30 Marks
15 Mins

__Concept:__

Schmidt number in mass transfer corresponds to the Prandtl number in heat transfer.

In heat transfer, Prandtl number (Pr) is a dimensionless number defined as the ratio of momentum diffusivity to thermal diffusivity. It is given as,

\(Pr = \frac{\nu }{\alpha } = \frac{{momentum\;diffusivity}}{{thermal\;diffusivity}} = \frac{{\mu /\rho }}{{k/\left( {{C_p}\rho } \right)}} = \frac{{\mu {C_p}}}{k}\)

where, m = Dynamic viscosity, cp= Specific heat, k= Thermal conductivity

In mass transfer, Schmidt number (Sc) is a dimensionless number defined as the ratio of momentum diffusivity (kinematic viscosity) and mass diffusivity. It is given as,

\(Sc = \frac{{viscous\;diffusion\;rate}}{{mass\;diffusion\;rate}} = \frac{v}{D} = \frac{\mu }{{\rho D}}\)

where, m = Dynamic viscosity, r = density and, D = mass diffusivity

Lewis Number represent the relative magnitudes of heat and mass diffusion in the thermal and concentration boundary layers.